Optical-chemical analyzes are the most common methods for determining the concentration of a solute in a solution, based on the ability of compounds to absorb or emit light energy of different wavelengths. Initially, visual colorimetry was used to compare the light emerging from a solution of an unknown concentration and the light emerging from a reference solution, until on the eyes of the observer, both emerging lights were identical (Garrigós L. and other. “Colorimeters” Universitat Politècnica de València. 2001). However, these results were subjective and inaccurate. Later in time, photocolorimeters were created, which consisted in a tungsten lamp where the light passed through a slit and then condenser lens, in order to obtain a parallel light beam incident on the unknown solution. Then, the lengths of the unabsorbed waves pass through a filter with a complementary color to the test solution, giving a monochromatic light. This light beam enters a photocell generating a small electrical current that increases through an amplifier, which signal is detected by a galvanometer delivering absorbance measurements. If a calibration curve is performed with standards or reference solutions, whose concentrations are known, versus the absorbance of each of them, one can determine the concentration of the solution by obtaining the absorbance. This technique is only useful when the solutions are colored, but other solutions which absorb in the range of ultraviolet light cannot be analyzed by a colorimeter. For the latter, a spectrophotometer that is capable of evaluating the absorption throughout the all UV/visible range is used. Furthermore, this equipment can distinguish between two compounds with a similar absorption, delivering absorption spectra that even allow the identification of the compounds that are being analyzed.
However, all these techniques require large and expensive equipment, so that the analysis of samples must be performed within a laboratory facility, impeding in-situ analyzes. To overcome these limitations, innovations have emerged that allow analysis of absorbance with camera phones, such as described by Z. Smith (Smith Z. et al. “Cell-Phone-Based Platform for Biomedical Device Development and Education Applications” PLoS One. 2011; 6(3):e17150), in which a grid and a collimator were attached to a cell phone camera generating an equipment sensitive to visible light between 350-650 nm. In another invention, Zhang J. (U.S. Pat. No. 8,537,343 B2) reduced the optics of the spectrometer, achieving a compact spectrometer of a wider range of light (UV, visible or infrared) which can be integrated into a cell phone or a portable electronic apparatus. Likewise, Wang S. (U.S. Pat. No. 7,420,663 B2) designed a device which is capable of measuring optical spectra, this device contains a laser or LED light source and a filtering element for a particular wavelength, which is detected and measured by a cell phone camera and the results are sent by a wireless network to a central control. There are also simpler inventions in applications that only analyze colored solutions, by impinging a light beam on the sample and obtaining a color numerical value or concentration. Such is the case of the invention of Thonhauser C. (U.S. Pat. No. 8,493,441 B2) which is a color sensing device attached to a portable electronic device that is configured to calculate the average values of discrete colors red, green and blue (RGB, red, green, blue) color processing in 8-bits per channel. This device requires that the sample is exposed to a light beam and detects the emitted wavelengths in the range of 400-700 nm. All mentioned inventions have the problem that they require an external device to the portable electronic apparatus for its use, which increases the cost of technologies and their access.
The present invention provides a practical and fast solution for analyzing concentrations of solutes in colored liquid solutions only using the integrated camera of a portable electronic device and configuring it to calculate the unknown concentration from the color evaluation of colored liquid samples whose concentrations are known, without the need to require an external measuring apparatus. This application can be useful for teaching basic concepts of chemical analysis in educational establishments, requiring only smartphone or tablet type devices, which are used by millions of people worldwide. The system calculates the concentration of a solute in a liquid solution from colored imaging which includes a calibration curve with known concentrations of liquid solutions and the sample or problem solution.